Check the Battery Back-up Unit (BBU) for Power
Note: The Battery Backup Unit (BBU) will shut down approximately one hour before that battery has completely drained. If you need to make an emergency phone call after the BBU has shut down, press the Battery Emergency Use button on the ONT. This should enable the ONT to reboot and provide up to one hour of talk time. After you press the Battery Emergency Use button, the BBU will operate until the battery has completely drained.